cceil

Implementation of ceil function in C

I have two questions regarding ceil() function..

  1. The ceil() function is implemented in C. If I use ceil(3/2), it works fine. But when I use ceil(count/2), if value of count is 3, then it gives compile time error.

    /tmp/ccA4Yj7p.o(.text+0x364): In function FrontBackSplit': : undefined reference toceil' collect2: ld returned 1 exit status

    How to use the ceil function in second case? Please suggest.

  2. How can I implement my own ceil function in C. Please give some basic guidelines.

Thanks.

Solution

  • The ceil() function is implemented in the math library, libm.so. By default, the linker does not link against this library when invoked via the gcc frontend. To link against that library, pass -lm on the command line to gcc:

    gcc main.c -lm